Means for controlling electric motors.



No. 672,4!9. Patented Apr. I6, I901.

F. A. JOHNSON.

MEANS FOR CONTROLLING ELECTRIC MOTORS.

(Application filed Jan. 15. 1901. L

2 Sheets'-Sheet lv No Model.)

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No 672,4l9. Patented Apr. l6, l90l. F. A. JOHNSON.

MEANS FOR CONTROLLING ELECTRIC MOTORS (Application filml km 1.5, 190).

No Mode UNITED STATES PATENT OEEICE.

FREDERIO AYRES JOHNSON, OF BINGHAMTON, NEW YORK, ASSIGNOR TO STOWMANUFACTURING COMPANY, OF SAME PLACE.

MEANS FOR CONTROLLING ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent No. 672,41 9, dated April16, 1901.

Application filed anuary 15, 1901.

To all whom it may concern:

Be it known that I, FREDERIO AYRES JOHN- SON, a citizen of the UnitedStates, residing at Binghamton, in the county of Broome and State of NewYork, have invented certain new and useful Improvements in Means for(Jontrolling Electric Motors, of which the following is a specification.

My invention relates to means for controlling electric motors, and whileit is intended more particularly for use in connection with motors itcan be used with electric generators.

The invention is based on the general principles set forth in my PatentNo. 597,418, granted January 18, 1898, and Ido not deem it necessary toagain set forth those principles further than. to explain that in thepresent invention mechanical means are provided whereby the reluctanceof the magnetic circuit is varied by simultaneously varying thereluctance of a portion of each pole-piece which may include one tip.The speed of the motor is thus varied, while the magnetic flux throughthose pole-tips under which commutation is taking place is maintainedsubstantially constant, sparking being thus avoided. Mechanical meansare also provided for varying the reluctance of the magnetic circuit bysimultaneously varying the reluctance of the central portions of thepole-pieces, while the flux through both tips of every pole ismaintained substantially constant.

While my invention may be applied to motors of various forms andconstructions with any number of field-magnet poles, I have shown it inconnection with a four-pole motor of the salient-pole type, and thiswill illustrate theinvention sufficiently to enable those skilled in theart to adapt it to any particular form of motor or generator.

In the accompanying drawings, Figure 1 is a side view, partly insection, of a motor embodying my invention. Fig. 2 is a longitudinalelevation of the motor. Fig. 3 is a side View, partly in section, of amotor embodying a modification of my invention. Fig. 4 shows amodification of the adjustable corepieces.

Serial No. 43,380. (No model.)

Referring to the drawings, A represents the armature, which may be ofany desired form and construction, provided with the usual commutatorCL, brushes b, and armature-shaft E, journaled in suitable bearings F.

B represents the field-magnet frame, with salient field-magnet poles 0,having tips 0 c and exciting-coils D. In each pole-piece O a cavity isformed of circularcross-section and preferably arranged with itsimaginary longitudinal axis substantially parallel to thearmature-shaft, so that the cavity is of cylindrical shape. Thesecavities may extend entirely through the frame B of the motor from sideto side, and they may also reach almost to the pole-facesf. Theirimaginary axes are preferably arranged to fall Within the outer side ofthe magnet-frame D, so that the opening d e of each cavity subtends anarc df e greater than a semicircle. Within the cavities are fitted.core-pieces P, of soft iron, each lacking a portion of a symmetricalvolume; but, as shown in Fig. 1, each lacks a segmental section, and inany case the cut surface should iie in or near the same plane as theouter surface of the frame, although this is not absolutely necessary,the essential feature being that the core-pieces P lack portions oftheir symmetrical volumes. The cut surfaces of the core-pieces may behollowed or made somewhat concave, as P in Fig. 4, instead of being madesubstan tially plane surfaces. The utility of this form of constructionwill hereinafter appear. It will be seen that when coils D are energizedby turning the core-pieces from the position shown in Fig. 1 in fulllines to that shown in dotted lines the reluctance of the magneticcircuit through a portion of each pole-piece is varied because of theair-gap g introduced in that portion. The magnetization through thispart of each pole-piece will fall and the speed of the motor willincrease; but the magnetization of pole-tips 0, under which commutationis taking place, will remain substantially unchanged, since the airgapdoes not extend to those tips, so that sparking will be avoided.

In order that the pole-pieces P may be sim ultaneously adjusted in thecavities through a limited angle, I have provided a system ofsuitably-connected levers and links. In this arrangement each core-pieceis provided with levers L, rigidly attached to one end thereof andplaced outside of the magnet frame. These levers are connected pivotallyat their outer ends it by connecting-links R, as shown, and a crank IIor other suitable mechanism is provided, attached to one pole-piece, bywhich the train of levers and links is actuated. It is therefore obviousthat any angular movement imparted to that core-piece to which the crankis attached will be simultaneously transmitted to every othercore-piece. In Fig. 3 is shown, however, a preferable mechanicalconstruction by means of which the core-pieces P may be simultaneouslyrotated to any desired degree, as through one hundred and eighty degreesfrom the position shown in full lines to that shown in dotted lines inFig. 3. Each core-piece is provided with a spur-gear Gr, attached to thecore-piece concentrically with its longitudinal axis, and supported inbearings h are rotatable shafts H, having worms h", meshing with thegears G. By turning a hand-wheel or other suitable device attached to aparticular shaft the core-pieces may be simultaneously adjusted in thecavities of the field magnet poles. When the core-pieces are rotatedthrough one hundred and eighty degrees into the dotted position of Fig.3, the magnetic flux through the centers of the pole-pieces will bevaried, while that through both tips of every pole will remainsubstantially unchanged, since the air-gap g" will fall somewhat withinthe tips.

By making the cut surfaces of the corepieces concave instead of planethe reluctance at the centers of the pole-pieces may be furtherincreased.

Grooves I, as shown in Fig. 4:, may also be cored through thepole-pieces in the cavities adjacent to the pole-tips and substantiallyparallel to the armature-shaft to prevent the comm utating-fiux in thepole-tips from diffusing itself through the centers of the polepieces.

My invention allows of rotation of the armature in either direction,that pole-tip which is to be kept at a substantially constantmagnetization depending, of course, upon the direction of rotation andupon whether the machine is being used as a motor or generator.

Without limiting myself to the precise details of construction shown anddescribed, which may be varied in details without departing from thespirit of my invention, what I claim, and desire to obtain by LettersPatent, is as follows:

1. In an electric motor, the combination with the frame, of field-magnetpoles having cavities, core-pieces in the cavities,and means forrotating the several corepieces in the cavities in the same direction,substantially as described.

2. In an electric motor, the combination with the frame, of field-magnetpoles having cavities. core-pieces in the cavities, means for rotatingsaid core-pieces in the cavities, and grooves in the cavities,substantially as described.

3. As a means of varying the reluctance of the magnetic circuit in anelectric motor, the combination with the frame, of field-magnet poleshaving cavities, core-pieces in the cavities, and means forsimultaneously adjusting said core-pieces in the cavities, substantiallyas described.

t. In an electric motor, the combination with the frame, and armatureand its shaft, of field-magnet poles having cavities, corepieces fittingthe cavities, and means for adjusting said core-pieces in the samedirection in the cavities about axes substantially parallel to thearmature-shaft, substantially as described.

5. In an electric motor, the combination with the frame, of field-magnetpoles having cylindrical cavities, core-pieces fitting the cavities, andmeans for simultaneously adjusting said core-pieces in the samedirection in the cavities, substantially as described.

6. As a means of varying the reluctance of the magnetic circuit in anelectric motor, the combination with the frame, and armature and itsshaft, of field-magnet poles having cylindrical cavities arrangedsubstantially parallel to the armature-shaft, core-pieces fitting thecavities, and means for adjusting said core-pieces in the cavities,substantially as described.

7. In an electric motor, the combination with the frame and armature andits shaft, of field-magnet poles having cylindrical cavities arrangedsubstantially parallel to the armature-shaft, core-pieces each lacking aportion of its symmetrical volume fitting the cavities, and means forsimultaneously adjusting said core-pieces in the cavities, the saidfieldmagnet poles having grooves in said cavities adjacent to thepole-tips and substantially parallel to the armature-shaft,substantially as set forth.

8. In an electric motor, the combination with the frame, of field-magnetpoles having cavities, core-pieces in the cavities, spurwheels connectedto the core pieces, and worms operatively connecting the spu r-wheels tosimultaneously rotate each spur-wheel and its core-piece in the samedirection, substantially as set forth.

9. In an electric motor, the combination with the frame, of field-magnetpoles having cavities, core-pieces in the cavities, spurwheels connectedto the core-pieces, shafts supported from the frame and provided withworms for engaging the spur-wheels, and

means for rotating one of the shafts, whereby In testimony whereof Ihave signed my the core-pieces are simultaneously adjusted name to thisspecification in the presence of IO in the same direction, substantiallyas detwo subscribing witnesses.

scribed. w

10. In an electric motor, the combination FREDERIC AYRES JOHNbON' withthe frame, of field-magnet poles having Witnesses: cavities, and groovesin the cavities adjacent F. W. JENKINS, to the pole-tips, substantiallyas described. J. F. LOUGHLIN.

